Static/dynamic storage - sticktion, oxidation, power cycling - CNET Storage ForumsThe short answer: do NOT rely on any single stored medium for important data. A failure could occur overnight or after years of storage. Place the data on different and redundant technologies, and store in physically different locations (ie; safe deposit box, friend's house, office, etc.). You may wish to encrypt prior to archival. Note that most safety deposit boxes are temperature/humidity controlled, and protected from fire.
Storing a drive on a shelf is not the same as continuing to use it, albeit intermittently. While mag-flux degradation as a function of time is a consideration, it is not the one most likely to cause problems in storage scenarios.
Some of the more significant variables in play for MAGNETIC disk media data recovery reliability are:
2) power-on/power-off cycling
3) oxidation (lubricants, medium, and components)
4) component 'seating'
Unfortunately, these can occur at ANY time, whether a drive is in use or on the shelf, however, these are less likely to appear while a drive is in use.
These can be very dependent on external environmental conditions and drive quality. Storing in a plastic bag could make things worse in some instances. It depends on the environment over time. It also depends on packing materials. There are some foams out there that over time emit corrosive gasses or contain contaminants that emit corrosive gasses. I've seen the faces of copper pennys COMPLETELY eaten away after only 2 years of storage in a container with apparently normal, dry, soft foam. Drive electronics typically contain a lot of copper, and other metals are also susceptible to these gasses.
1) sticktion ---
Whenever some drives are powered off, there is a small chance for a phenomenon called ''sticktion'' to appear. This occurs when the r/w head(s) are left in contact with a single place on the drive platter surface for a period of time. It can occur after as little as a day, or as long as 10 years. The problem is that the r/w head(s) settle into the medium and become effectively ''glued'' to the medium's surface, and when the drive spins-up, it can either rip a chunk of recording media off the platter, and in the worst cases, rip the r/w head out of the actuator. Either way, you now have huge bits of material freely moving inside your disk drive, and it will eventually cause additional r/w failures.
MOST drives these days park the r/w head(s) so it is physically NOT touching the drive platter(s)and sticktion is not even a problem. Older drives are more susceptible to this problem. However, SOME manufacturers still ''park'' the r/w heads on the platters to reduce manufacturing costs.
2) power cycling, oxidation, and seating ---
Whenever a drive is powered on, there is an increased chance of drive failure when it is powered-on. Usually the motor driver electronics. This is often due to motor startup current requirements. This is more often the case at non-nominal power supply limits, and again, with older drives. Newer drives have generally done a lot of engineering to reduce this problem, but it still occurs.
It should be noted that after being inactively stored for a number of years, hard drive internal lubricants (where used) can evaporate or partially solidify. Self-lubricating plastics can deteriorate. Parts that move against each other may partially oxidize, or seat themselves in such a way as to cause increased friction between some parts when the drive is powered on. This can result in electronics failure (due to excessive current), physical component damage (as one part rips another from its proper alignment).
Remember that the ability to reliably read the data is dependent on alignment tolerances in anywhere from microns to thousandths of an inch, depending on the part involved. Generally speaking, the higher capacity the drive, the tighter tolerances required.
For example, in some cases, I've seen the head parking lock mechanism oxidize to the point where it won't disengage. I've also seen instances where the platter and/or medium themselves oxidized (this was during extreme prolonged cases of storage heat and humidity).
Remember also, that POH (Power On Hours) needs to be considered in conjunction with power on-off cycling. A drive that is spec'd to run for 100,000 hours if just turned on once and left running, might fail after 100 hours if it is power-cycled every 5 minutes. Specmanship is an art to the manufacturers, and the more drive manufacturers are driven to reduce costs, the more they are driven to be creative with specs.
Also, in the case of any moving storage media, when taking out of storage and placing into service, be sure to let the device acclimate to the current temperature and humidity. For example, if you bring a drive from a cooler storage location to a warm, humid location, condensation may develop on the internal drive components and when you power-up, it can damage the data and/or drive. If the data are important, you would probably want to wait at least several hours before powering-up the drive. Some folks recommend waiting overnight.